arch/riscv: Refactor bootblock.S

A few things are currently missing:
- The trap handler doesn't set the stack pointer, which can easily
  result in trap loops or memory corruptions.
- The SBI trampolin page (as described in version 1.9 of the RISC-V
  Privileged Architecture Specification), has been removed for now.

Change-Id: Id89c859fab354501c94a0e82d349349c29fa4cc6
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/15591
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

3 files changed, 55 insertions, 124 deletions

diff --git a/src/arch/riscv/Makefile.inc b/src/arch/riscv/Makefile.inc
index c1c62efb7c..718aad9582 100644
--- a/src/arch/riscv/Makefile.inc
+++ b/src/arch/riscv/Makefile.inc
@@ -28,6 +28,9 @@ endif
 ################################################################################
 ifeq ($(CONFIG_ARCH_BOOTBLOCK_RISCV),y)
 
+bootblock-y += id.S
+$(call src-to-obj,bootblock,$(dir)/id.S): $(obj)/build.h
+
 bootblock-y = bootblock.S stages.c
 bootblock-y += trap_util.S
 bootblock-y += trap_handler.c
diff --git a/src/arch/riscv/bootblock.S b/src/arch/riscv/bootblock.S
index 5092ec0405..514511ed0d 100644
--- a/src/arch/riscv/bootblock.S
+++ b/src/arch/riscv/bootblock.S
@@ -1,7 +1,8 @@
 /*
- * Early initialization code for aarch64 (a.k.a. armv8)
+ * Early initialization code for RISC-V
  *
  * Copyright 2013 Google Inc.
+ * Copyright 2016 Jonathan Neuschäfer <j.neuschaefer@gmx.net>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -13,7 +14,7 @@
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.See the
  * GNU General Public License for more details.
  */
-// See LICENSE for license details. relating to the _start code in this file.
+
 #include <arch/encoding.h>
 
 .section ".text._start", "ax", %progbits
@@ -24,130 +25,24 @@ _start:
 #define STACK_START 0x80800000 /* 2GiB + 8MiB */
 #define STACK_SIZE  0x0000fff0
 
-	// pending figuring out this f-ing toolchain. Hardcode what we know works.
-  li sp, STACK_START + STACK_SIZE
-
-  # make room for HLS and initialize it
-  addi sp, sp, -64 // MENTRY_FRAME_SIZE
-  csrr a0, mhartid
-  call hls_init
-
-  //poison the stack
-  li t1, STACK_START
-  li t0, 0xdeadbeef
-  sd t0, 0(t1)
-
-  la t0, exception_handler
-  csrw mtvec, t0
-
-  # clear any pending interrupts
-  csrwi mip, 0
-
-  # set up the mstatus register for VM
-  call mstatus_init
-  call main
-.=0x2000
-    .space 0x800
-# sbi interface lives here
-
-# hart_id
-.align 5
-li a7, 0
-ecall
-ret
-
-# num_harts
-.align 4
-li a0, 1
-ret
-
-# query_memory
-.align 4
-li a7, 8
-ecall
-ret
-
-# console_putchar
-.align 4
-li a7, 1
-ecall
-ret
-
-# send_device_request
-.align 4
-li a7, 2
-ecall
-ret
-
-# receive_device_response
-.align 4
-li a7, 3
-ecall
-ret
-
-# send ipi
-.align 4
-li a7, 4
-ecall
-ret
-
-# clear ipi
-.align 4
-li a7, 5
-ecall
-ret
-
-# timebase
-.align 4
-li a0, 10000000 # temporary, we should provide the correct answer
-ret
-
-# shutdown
-.align 4
-li a7, 6
-ecall
-
-# set_timer
-.align 4
-li a7, 7
-ecall
-ret
+	li sp, STACK_START + STACK_SIZE
 
-# end of SBI trampolines
-.=0x4000
-.stack:
-.align 8
-	.space 0xf00
-.stacktop:
-	.quad 0
-.align 3
-.stack_size:
-	.quad 0xf00
-.globl test_trap
-exception_handler:
-        call trap_handler
-reset:
-init_stack_loop:
+	# make room for HLS and initialize it
+	addi sp, sp, -64 // MENTRY_FRAME_SIZE
+	csrr a0, mhartid
+	call hls_init
 
-	.word CONFIG_STACK_SIZE
-	.section ".id", "a", %progbits
+	# poison the stack
+	li t1, STACK_START
+	li t0, 0xdeadbeef
+	sd t0, 0(t1)
 
-	.section ".id", "a", @progbits
+	la t0, trap_entry
+	csrw mtvec, t0
 
-	.globl __id_start
-	// fix this bs later. What's wrong with the riscv gcc?
-__id_start:
-ver:
-	.asciz "1" //COREBOOT_VERSION
-vendor:
-	.asciz "ucb" //CONFIG_MAINBOARD_VENDOR
-part:
-	.asciz "1" //CONFIG_MAINBOARD_PART_NUMBER
-.long __id_end + CONFIG_ID_SECTION_OFFSET - ver  /* Reverse offset to the vendor id */
-.long __id_end + CONFIG_ID_SECTION_OFFSET - vendor  /* Reverse offset to the vendor id */
-.long __id_end + CONFIG_ID_SECTION_OFFSET - part    /* Reverse offset to the part number */
-.long CONFIG_ROM_SIZE                               /* Size of this romimage */
-	.globl __id_end
+	# clear any pending interrupts
+	csrwi mip, 0
 
-__id_end:
-.previous
+	# set up the mstatus register for VM
+	call mstatus_init
+	tail main
diff --git a/src/arch/riscv/id.S b/src/arch/riscv/id.S
new file mode 100644
index 0000000000..798aa8967c
--- /dev/null
+++ b/src/arch/riscv/id.S
@@ -0,0 +1,33 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <build.h>
+
+	.section ".id", "a", %progbits
+
+	.globl __id_start
+__id_start:
+ver:
+	.asciz "1" //COREBOOT_VERSION
+vendor:
+	.asciz "ucb" //CONFIG_MAINBOARD_VENDOR
+part:
+	.asciz "1" //CONFIG_MAINBOARD_PART_NUMBER
+.long __id_end + CONFIG_ID_SECTION_OFFSET - ver  /* Reverse offset to the vendor id */
+.long __id_end + CONFIG_ID_SECTION_OFFSET - vendor  /* Reverse offset to the vendor id */
+.long __id_end + CONFIG_ID_SECTION_OFFSET - part    /* Reverse offset to the part number */
+.long CONFIG_ROM_SIZE                               /* Size of this romimage */
+	.globl __id_end
+
+__id_end:
+.previous